JPH0361749A - Feed screw mechanism - Google Patents

Abstract

PURPOSE:To increase the power transmission efficiency while maintaining precision, obtain a simple and lightweight feed screw mechanism, facilitate assembling and disassembling, and reduce the production cost by integrating a wheel with a moving piece linearly moved only in the axial direction of a screw shaft via a bearing. CONSTITUTION:The outer periphery of a wheel 2 is coupled in contact with the screw groove (a) of a screw shaft 1, and the axis (b) direction of the wheel 2 is made perpendicular to the direction of the helix of the screw shaft 1. The angle alpha between the axis (b) of the wheel 2 and the axis (c) of the screw shaft 1 is equal to the lead angle of the screw shaft 1. The outer periphery of the wheel 2 coupled with the screw groove (a) is correctly engaged with the screw groove (a) invariably in stable contact when the wheel 2 is rotated. The wheel 2 is supported by a bearing 3, and the bearing 3 is fixed on a moving piece 4. The moving piece 4 is guided by a guide 5 installed in parallel with the screw shaft 1 and can be moved, but it is restricted by the guide 5 not to be rotated or vertically moved. When the screw shaft 1 is positively or reversely rotated by a motor 6, the moving piece 4 is guided by the guide 5 and reciprocated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application The present invention belongs to the field of mechanical elements that transmit power and convert modes of motion.

BACKGROUND ART In recent years, there has been an extremely high demand for feed drive mechanisms used in various precision machines, machine tools, transportation and assembly machines, robots, office machines, and the like.

There are many types of feed screws, but they can be broadly divided into sliding contact feed screws, rolling contact feed screws, and non-contact feed screws.

Sliding contact lead screws wear quickly and are inefficient.

A typical non-contact feed screw is a static pressure feed screw, but it has the disadvantage of being difficult to manufacture.

A typical rolling contact lead screw is a ball screw. Ball screws have a complex structure because they require a circulation path for the balls, and the assembly work for inserting the balls is not easy.Furthermore, during use, many balls roll in contact with each other, so the contact points are Sliding resistance occurs in the direction of the ball, and the sliding resistance between the circulation path wall and the ball cannot be ignored.

The present inventor has previously applied for a patent (Application No. 63-211707) as a mechanism that eliminates these drawbacks, but similar to the ball screw system, the movable piece (nut) that holds the screw shaft moves. There is no difference.

Mechanisms that hold screw shafts tend to be large in size and require time and effort to assemble and disassemble.

As a mechanism in which the movable piece does not hold the screw shaft and does not have the above-mentioned disadvantages of the ball screw, there is a spindle shaft mechanism shown in U.S. Pat. There is a mechanism in which a wheel is used as a moving piece, the axis of the moving piece is parallel to the screw shaft, and the ring groove and the screw shaft are engaged.

However, since the screw direction of the ring and the screw shaft do not match, they do not mesh accurately and do not come into surface contact, so they are prone to wear and tear. The present inventor has previously applied for a patent (Application No. 63-269832) as a method to overcome this drawback, but this mechanism is inferior in accuracy.

As described above, various types of feed screw mechanisms have been used to date, but each has its own advantages and disadvantages.

Purpose of the Invention The present invention has a simple mechanism, is light and small, is easy to set up and disassemble in the morning, is relatively inexpensive to manufacture, and has little wear and tear during use.
The present invention provides a device that converts forward and reverse rotation of a screw shaft into reciprocating motion of a moving piece.

Configuration of the Invention and Disclosure Based on Drawings FIGS. 1 and 2 are exemplary diagrams of the present mechanism for explanation, and FIG. 1 is a front view. FIG. 2 is a plan view, with some parts omitted for ease of understanding.

In FIGS. 1 and 2, the outer peripheral portion of the wheel (2) fits into and contacts the screw groove (a) of the screw shaft (1). The direction of the axis (b) of the wheel (2) is perpendicular to the direction of the helical line of the screw shaft (1). That is, the angle α between the axis (b) of the wheel (2) and the axis (c) of the screw shaft is equal to the lead angle of the screw shaft. Therefore, the wheel (2) fitted in the screw groove (a)
Even when the wheel (2) rotates, the outer peripheral portion of the wheel (2) always meshes accurately with the threaded groove (a) and is in stable contact with the threaded groove (a).

The wheel (2) is supported by a bearing (3).
) is fixed to the movable piece (4).

The movable piece (4) can move guided by a guide (5) installed parallel to the screw shaft (1), but at the same time, the movable piece (4)
5) restricts other movements, such as rotation and vertical movement.

When the screw shaft (1) is rotated forward and backward by the motor (6), the moving piece (4) is guided by the guide (5),
Move back and forth.

The mechanism of the present invention is a ball screw, patent M (application number 6).
3-211707), it is simpler, lighter, smaller, easier to assemble and disassemble, and has higher precision.

Furthermore, unlike in a ball screw, there is no sliding resistance in opposite directions at the contact points of the aligned balls, so the power
Transmission efficiency is also high.

Of the lead accuracy listed in JIS B 1192, 3 is arbitrarily taken between the effective screw length of the screw shaft.
When the moving piece according to the mechanism of the present invention and the ball screw were compared with respect to the variation with respect to 0.00 mm, it was found that there was no significant difference.

As illustrated in FIGS. 3 and 4, the mechanism of the present invention allows two or more wheels (2) to face each other with respect to a helical shaft (1), or They can also be arranged side by side and fixed to a common moving piece (4) via a bearing (3).

FIG. 5 shows an example in which two wheels are used and a spring (7) etc. is installed between them to apply a predetermined preload. Applying preload reduces the axial clearance and increases repeatability. In addition, as a method of applying preload, the wheel (2) is pressurized with a spring or the like so as to face the axis (C) of the screw shaft (1), so that both sides of the outer circumference of the wheel (2) are always kept in the screw groove ( It may be made to contact both walls of the concave cross section in a).

Although not shown in FIGS. 1 and 3 to 5,
The axis of the wheel (2) is inclined in a direction perpendicular to the plane of the paper by the lead angle of the screw shaft (angle α in FIG. 1).

The type of bearing (3) is not necessarily as shown in Figure 1, Figure 2, or Figure 3.
In addition to the example shown in the figure or FIG. 4, a ball 9) or roller may be arranged between the wheel (2) and the axle (8) as shown in FIG. 6. It is also possible to use a sliding bearing.

FIG. 7 shows an example of the mechanism of the present invention using two so-called cam floors. Furthermore, an example using a cantilever bearing may also be considered.

Various cross-sectional shapes and inclinations of the wheels can be selected, such as those illustrated in FIG. 8.

The above explanation was about the case where the screw shaft was fixed and the movable piece moved linearly, but when the movable piece was fixed,
It will also be readily understood that the screw shaft moves linearly in its axial direction. Therefore, the linear movement of the moving piece in the present invention should be interpreted as relative linear movement with the screw shaft.

Effects of the Invention The present invention maintains the accuracy of ball screws that are widely used in conventional products, has high power transmission efficiency, is simple, light and small, is easy to assemble and disassemble, and has a low manufacturing cost. It provides a screw mechanism.

[Brief explanation of drawings]

FIG. 1 is a front view of an example of a feed screw mechanism according to the present invention, and FIG. 2 is a plan view with some parts thereof omitted. Fig. 3 shows the case where the moving piece has two wheels and they are arranged facing each other across the screw shaft, and Fig. 4 is an explanatory diagram when they are arranged side by side in the axial direction of the screw shaft. . FIG. 5 shows a cut hole when two wheels are pressurized by a spring in opposite directions in the axial direction of the screw shaft. FIG. 6 shows a cutout in the case where the bearing type is one in which balls are arranged between the wheel and the axle. FIG. 7 shows the cutting hole when two cam floors are used. FIG. 8 shows various examples of cross sections of wheels. In Figures 1 to 8, ・Screw shaft, bearing, guide, spring, ball, screw groove, axis of screw shaft 2 ・ 4 ◆ 6 ・ 8 ・ lO・ b ・ ・Wheel, moving piece, motor, axle, Cam floor - Wheel axis

Claims (1)

[Scope of Claims] 1. A rotatable screw shaft and a rotatable wheel having a shape in which a part of the outer circumference fits into one of the thread grooves of the screw shaft, such that the direction of the axis of the wheel is A feeder characterized in that the wheel is integrated with a moving piece that is meshed perpendicularly to the direction of the helical line of the screw shaft and that can move linearly only in the axial direction of the screw shaft through a bearing. Screw mechanism. 2. The feed screw mechanism according to claim 1, which includes two or more wheels.